Device for suppressing pulsations in fluid streams



xR 291549223 V I '1 1 April 11,1939. I H. N. m 2,154,223

DEVICE FOR SUPPRESSING FULSATIONS IN FLUID STREAIS Filed Oct 26.. 1956 HENRY N.WADE I v 3 4' INVENTOR tion The primary object of my invention is to provide means for dampening the pulsations produced influid conveying lines by the operation o! the pumps or compressors by which the fluid is supplied to the line A corollary object of my invention is to provide means for obtaining accurate readings from flow meters located in proximity to air and gas compressors and in the lines attached to them.

It is well known that pumps oi the reciprocah ing type handling either liquids or gases produce a pulsating iiow and that this pulsation is feltonboth thesuction and the disch2:- side of the pump. "It is also well known that these pulsations are transmitted through pipe lines to considerable distances :Iro'm their source, specifical ly,-to such distance as to permit the elasticity of the fluid, in the case of a gas, or o! the system in which it is confined. in' the case of a liquid,

so to absorb the variation in pressure occasionw by the stroking ot the pump.

In the case of liquids the pulsation of the stream i's-i'elt mainly as afhammer which may be highly destructive to pipe and fittings, but

. in theoperation or a gas compressing systempuls'ation is objectionable mainly in that it renders diiiicult the metering of the gas stream at or adjacent either end of the compressor.

The meters used on large gas flows are usually 30.01 the oriflce type, and whensuch meters are installed in the path of a pulsating gas flow they read "over" to an extent varying with the severity oi the pulsation and which may be as great as 60% to 80% over the true reading. The actualv extent of this error is immaterial as, no matter how small, it is variable with certain variations in operating conditions which are out ,0! control. For this reason the error cannot be eliminated bythe application of any predetermined correction factor. Obviously a meter reading containing an unknown and variable error is totally worthless.

Heretoiore dependable meter readings have been obtained by one of two expedients. The

first is to place the meter at such distance from the compressor that the elasticity of the gas in the line will absorb the pulsations and produce a flow-having constant velocity at the point where uit enters the meter. This distance is usually so so great thatthe meter is practically useless to the station attendants to whom its indications are or the greatest use. The other expedient is to shorten the distance by placing a surge tank in the line and so throttling i1.-.2 outlet as to pro- Bii duce uniform velocity downstream from the UNITED STATES I DKIVIGE FOB M11088 l N. Wade, Loo Ans lm Parkhm-Wcde. In Angeles, Calif, ac na licant-lawnmower! 1mm 9Cl aims. (miss-so throttiingpoint. Tomakethisseconddevice' effective the surge tank must be 01 large capacity and the pressure drop through the throttle considerable, resulting in an undesirable item of iniiialexpenseandasetiouswasteoipowerin g ccmpression..- v Y .I have discoveredthat it is possible to com:-

- pleiely eliminate pulsation at a point which may,

if desirecibe immediately adjacent the pump or compressor. by interposing in the flow line re- 1| sistance which comes into eflect only when the flow tends to increase and disappears during that portion of the pump cycle during which the flow tends to decrease, and that elimination of pulsation in this manner may be accomplished with 18 onlya slight and immaterial throttling oi theilow and consequently with an immaterial increasein power consumption over that observed when pulsation is permitted. V.

A device adapted to the application 01 this 20 principle in the pumping or compression of gases is diagrammatically shown in the attached draw- 1118-,- it being rmderstood that'this' drawing is illustrative only and subject to modification in many respects. 28

In the specific form illustrated the device 0011- sists of acylindrical chamber divided into the three chambers ill, U and ii. The inlet gas pipe 83 connects directly into the middle chamber ll. This chamber isseparatedfrom the upa per chamber ill by a flexible diaphragm N. 111e- Iull equivalent of this diaphragm would'be a loose fittingand light metallic piston.

Lower chamber [2 communicates directly with the outlet gas line IS in which. in this instance. 85 the orifice meter would be inserted. Chamber I! also with chamber H through the annular valve seat l5 which partially separates these two chambers. This opening is partially obstructed by a floating valve I'I, shown 49 as conical but which may be of any other form, this valve being suspended from diaphragm II by means of a rigid rod IS. The valve may be held in alignment by any iorm of guide not shown. I 45 Valve i7 is normally urged toward-its closed position in seat l5 oy a spring I, thetension of which may be adjusted by a turn-buckle 2! passing through the head 2| and covered by a gas-tight cap 22. I a

A pipe 22 including a throttling valve 2| at lords osmmunication. by way or inlet pipe I! or otherwise, between the upper and middle chambers II and I2.

The device above described is operated by mo ss- PATENT orrica' 1 in. the inlet pipe rises above'normal-and '5 in an direction when the pressure falls below normal. me space between the valve and its seat, through which gas flows, 'irom'the inlet .0 the outlet p pe. is thus restricted as the pressure rises and enlarged as it tails, and the variation in tree area thus produced may, with proper adjustment or the controls, be caused to exactly P compensate the variations in pressure upstream of the valve and thus produce uniiormity of how through the valve opening and, by consequence.

uniiormiw of pressure in the lower chamber and To develop this in more-detaiL- we mavnrst assume a condition of no pulsation. in whichthe inthe inlet pipe isuniiom' Chaingas .20 hers ii and i2 being in communication through pipe 23 (valve 2| being at least partially open) the the diaphragm will be free to move in either directionunder the influence of any other force.

25 'Ihisiorce isthepressure oi the gasinchamber il acting on the upper surface of valve i1 and opening it against the lilting action of spring 19. The valve thus throttles the normal flow of gas to an extent governed by the tension 01 the spring, which may desirably be made very low by suitable selection and adjustment.

We will assume next a condition or rapidly rising pressure in the inlet Pipe. Such as is produced by the rising side of a pulsation wave. Chamber l'l, being in iull communication with the inlet pipe. is subjected instantly to the increased pressure. Chamber l0, communicating with the inlet pipe only through the restricted opening provided by valve 24', comes to the in- 40 creesa'ipressure more slowly. momentarily the I pressures on the two faces 01 the diaphragm are unbalanced, the greater pressme being on its lower side. The diaphragm being oi much greater area than valve I'I. the diaphragm moves up- 5 wardly, carrying the valve with it and decreasing the tree area 0! valve opening and thus increasing the throttling action of the valve.

Ihs upward movementterminates when the were in chamber ill has risen, by flow or gas through valve 24, to such level that the total pressure on the upper face of the diaphragm plus the total pressure on the upper face of valve l'l equals the pressure on the lower !ace 0! the diaphragm plus the pressure on the lower race of the valve At this point the pressure in chambe: it is still somewhat below the pressure in chamber ii, and the movement is reversed in dimction as the pressure in the upper chamber approaches equality with that in chamber ll. so when these pressures havebecome equal zed the valve will have returned to the position which [it would occupy. for any given. rate 0! gas flow, under the condition of. no pulsation. The drop in pressure corresponding to the fallins side or the pulsation wave produces the reverse of the above movements. 'Ihemomentarily unbalanced. pressure is exercised on the upper side of the diaphragm. the valve is carried downwardly or in an opening direction, and the throttling action of the valve is momentarily reduced or eliminated. 1

-Thus the cycle for a single pulsation wave is one in which a valve having normally are! tivcly small throttling action on the gas flow is it causal to exercise an increased resistance by in- "sides diaphragm-ll; by jwhich it'jseaused to "move valve-l1 in .aclosingfiireoiion when the; I I

' 'this devicetopressure changes L *proportion to the waightot the moving put! 5 v est pcmible terms. valve ll restricts the flow of gas between the inlet 1.

V tent or the-response, I1. e., oi travel for m in a closing direction at times when said M Q inthesechamberswillbeequaiandstricting said flow; means arranged to 'move said .by decreased-inlet p It will be evident that the responsiveness cl will be reduced u and for this reason the mass 0! diaphragm ll, rod ll and valve II should be held to the smil This being done, the rate at response will be governed by the extent to which pe and the upper chamber, increased restriction reducing; the speed ot response to pressure changes and likewise increasing" the lineal e!- Iehimasmri e t on: j v p 1. In apparatus tor-dampening ulsations in a flowing stream of fluid:- a valve norms-ll! restricting said flow; means for moving said valve tends to increase and in an opening direction at times when said flow tends to decrease, and means for adjusting the speed oi response oi said valve moving means to changesin rate oi flow. 1 2. 1n apparatus for dampening pulsations in a flowing stream or fluid:- a valve normally revalve in a closing direction in response to increase in pressure upstream from said valve and in an opening direction in response to decrease in said a pressure, and means for adjusting the ct response oi said valve moving means to said pres'mre changes. v

3. In apparatus tor dampening pulsations in a flowing stream of fluid: a valve interposed in the a path ct said stream: a chamber'and-a movable element therein, said" element being operative]! chamber being in free fluid communication with said stream on one side oi said element, and a controllably restricted means of communication between said stream and the portion of said chamber on the other side of said element.

4. In apparatus for dampening pulsations in a flowing stream of fluid: a substantially closed 45 flowing stream of fluid: a substantially closed 5:

hollow body and a flexible diaphragm dividing said body into two. chambers; fluid inlet and outlet pipes communicating with one o! saidchambers; an outwardly opening valveinteposed in;

said outlet; a stem connecting said valve with a said diaphragm; a fluid channel connecting said chambers, and a manually operable valve inter. P sed in said fluid channel.

- 6. In apparatus for dampening pulsations in a flowing stream of fluid: a valve arranged in the g path of said flow; a movable element arranged to take the pressure. of said flowing stream on both 0! its sides; an operative connection between said valve and said movable element whereby ope i and closing movements of saidvaivc are eflected 7.

'Iby unbalancing of pressure on the two sides of said element, and reguiahle means for equalizing momentary unbalancing of said prssure.

7. Apparatus for dampening pulsations in a flowing stream r fluid, comprising: throttling e i a m more path oi mo sistan'e'eofiered by said throttling mums in relation to 'the rates oi respective increase and decrease in pressure upstream irom said throttling means, and means (or remrnin: said throttiinz means to a predetermined normal position after apreasurechanaeinoniyone direction.

8. Apparatua or dampening pulsations in a flowing stream e! fluid, comprising: n variabie resistance-means interposed in the path of said stream: means for increasing and decreasing the extent of the resistance ofleredhyaaid variable;

means in response respective to ciecreaaein ressureupstreairiiromaaicivariabie miiaaaa' stream; means for increasing and decreaainzwthe now re means !or returning said resistor to a prede is maintained.

HENRY N. WADB 

